[PATCH v3 01/15] PCI/MSI: Forward MSI-X vector enable error code in pci_alloc_irq_vectors_affinity()

Piotr Stankiewicz
2020-06-09T09:15:34Z

When debugging an issue where I was asking the PCI machinery to enable a
set of MSI-X vectors, without falling back on MSI, I ran across a
behaviour which seems odd. The pci_alloc_irq_vectors_affinity() will
always return -ENOSPC on failure, when allocating MSI-X vectors only,
whereas with MSI fallback it will forward any error returned by
__pci_enable_msi_range(). This is a confusing behaviour, so have the
pci_alloc_irq_vectors_affinity() forward the error code from
__pci_enable_msix_range() when appropriate.

Signed-off-by: Piotr Stankiewicz <piotr.stankiewicz@intel.com>
---
drivers/pci/msi.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 6b43a5455c7a..cade9be68b09 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1191,8 +1191,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
struct irq_affinity *affd)
{
struct irq_affinity msi_default_affd = {0};
- int msix_vecs = -ENOSPC;
- int msi_vecs = -ENOSPC;
+ int nvecs = -ENOSPC;

if (flags & PCI_IRQ_AFFINITY) {
if (!affd)
@@ -1203,17 +1202,16 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
}

if (flags & PCI_IRQ_MSIX) {
- msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,
- max_vecs, affd, flags);
- if (msix_vecs > 0)
- return msix_vecs;
+ nvecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
+ affd, flags);
+ if (nvecs > 0)
+ return nvecs;
}

if (flags & PCI_IRQ_MSI) {
- msi_vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs,
- affd);
- if (msi_vecs > 0)
- return msi_vecs;
+ nvecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, affd);
+ if (nvecs > 0)
+ return nvecs;
}

/* use legacy IRQ if allowed */
@@ -1231,9 +1229,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
}
}

- if (msix_vecs == -ENOSPC)
- return -ENOSPC;
- return msi_vecs;
+ return nvecs;
}
EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);

--
2.17.2